Regioselective acylation of d-ribono-1,4-lactone catalyzed by lipases

AbstractLipases from ten different sources and two mycelium-bound lipases isolated from Amazonian fungi were screened as biocatalysts in the acylation reaction of d-ribono-1,4-lactone with a variety of acyl donors in non-aqueous media. Several reaction parameters were evaluated including the type and amount of enzyme, acyl donor, and organic solvent, as well as the influence of water and the recyclability of the catalyst. When Candida antarctica lipase (CAL-B) was used, the acylation was highly regioselective and the corresponding 5-acyl-d-ribono-1,4-lactones were observed as the sole product. The best conversion (>99%) into 5-acetyl-d-ribono-1,4-lactone was obtained through the combination of vinyl acetate as the acetyl donor and 10mg (100U) of CAL-B in dry acetonitrile after 24h. However, lipases from Burkholderia cepacia (PSL-C and PSL-D), Pseudomonas fluorescens (AK) and Thermomyces langinosus (Lipozyme TL-IM) gave mixtures of mono-, di- and tri-acetylated products in lower conversions. CAL-B maintained its catalytic activity during five cycles of repeated use when decanoic and dodecanoic acids were employed as acyl donors in the acylation of d-ribono-1,4-lactone

(E,E)-Methyl 2-[(3-nitrobenzylidene)­aminomethyl]-3-phenylpropenoate

The mol­ecule of the title compound, C18H16N2O4, adopts a T-shaped conformation with E stereochemistry for the imine double bond. The (3-nitro­benzyl­idene)amino fragment is almost planar, the mean planes of phenyl ring and nitro group forming a dihedral angle of 8.9 (3)°. In the 3-phenyl­acryloyl unit, the acrylic ester fragment is also almost planar, with the phenyl ring twisted by 41.44 (7)°. In the crystal, the mol­ecules are linked by C—H⋯O hydrogen-bond inter­actions into chains running parallel to [01]

Synthesis of novel O-acylated-D-ribono-1,5-lactones and structural assignment supported by conventional NOESY-NMR and x-ray analysis

A practical method for the structural assignment of 3,4-O-benzylidene-D-ribono-1,5-lactones and analogues using conventional NMR techniques and NOESY measurements in solution is described. 2-O-Acyl-3,4-O-benzylidene-D-ribono-1,5-lactones were prepared in good yields by acylation of Zinner’s lactone with acyl chlorides under mildly basic conditions. Structural determination of 2-O-(4-nitrobenzoyl)-3,4-O-benzylidene-D-ribono-1,5-lactone was achieved by single crystal x-ray diffraction, which supports the results based on spectroscopic data.Este trabalho apresenta um método simples para a caracterização estrutural de 3,4-O-benzilideno-D-ribono-1,5-lactonas e análogos, fundamentado em técnicas convencionais de RMN e experimentos de NOESY em solução. 2-O-Acil-3,4-O-benzilideno-D-ribono-1,5-lactonas foram preparadas em bons rendimentos a partir da acilação das lactonas de Zinner empregando cloretos de ácido sob condições básicas. A estrutura de 2-O-(4-nitrobenzoil)-3,4-O-benzilideno-D-ribono-1,5-lactona foi determinada por difração de raios-X e confirmou, de forma inequívoca, os dados espectroscópicos obtidos.CNPq - MC

Simple method for fast deprotection of nucleosides by triethylamine-catalyzed methanolysis of acetates in aqueous medium

A straightforward methodology for deacetylation of protected ribonucleosides was developed based on triethylamine-catalyzed solvolysis in aqueous methanol. Reactions are completed in a few minutes under microwave irradiation and the free nucleosides are obtained in high yield after simple evaporation of volatiles. Other important features include the involvement of readily available reagents and the compatibility with diverse functional groups, which make this process very attractive for broad application

5-O-Acetyl-d-ribono-1,4-lactone

The title compound, C7H10O6, was obtained from a regioselective enzyme-catalysed acyl­ation of d-ribono-1,4-lactone. The five-membered ring of the acyl­ated sugar shows an envelope conformation. In the crystal, the mol­ecules are linked by inter­molecular O—H⋯O hydrogen-bonds, forming a one-dimensional polymeric structure parallel to [010]. In addition, packing analysis shows stacking along the b axis

Genome Sequence of Corynebacterium pseudotuberculosis MB20 bv. equi Isolated from a Pectoral Abscess of an Oldenburg Horse in California.

The genome of Corynebacterium pseudotuberculosis MB20 bv. equi was sequenced using the Ion Personal Genome Machine (PGM) platform, and showed a size of 2,363,089 bp, with 2,365 coding sequences and a GC content of 52.1%. These results will serve as a basis for further studies on the pathogenicity of C. pseudotuberculosis bv. equi

Síntese e caracterização de arcabouços de quitosana com agente antineoplásicos

O sistema de liberação controlada de fármacos através da utilização de biomateriais poliméricos associados a compostos com ação antineoplásica pode ser empregado como alternativa de tratamento de neoplasias. Desta forma, este trabalho teve como objetivo a síntese e caracterização de sistemas de arcabouços de quitosana com o agente antineoplásico (1,4-naftoquinona), cuja taxa de liberação pode ser controlada pela utilização de um agente reticulante como o tripolifosfato de sódio (TPP). O método de preparação consistiu da solubilização da quitosana em ácido acético, adição do fármaco, congelamento, liofilização e reticulação com TPP. Todas as amostras foram caracterizadas por Difração de Raios X (DRX), Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Energia Dispersiva de Raios X(EDS), grau de intumescimento e biodegradação enzimática. Na MEV foi evidenciada a formação de poros interconectados com tamanhos e formas variadas em todas as estruturas estudadas caracterizando a formação de arcabouços. Já no EDS foi observada a presença de elementos químicos característico da composição química de cada material. No entanto foi observada a presença do sódio que pode estar relacionado ao agente neutralizante utilizado. A reticulação de parte dos arcabouços foi comprovada pelo DRX, EDS e aumentou a taxa de degradação enzimática in vitro dos mesmos. A incorporação do fármaco foi confirmada por DRX, grau de intumescimento e EDS. Desta forma, pode-se concluir que ocorreu à formação de arcabouços reticulados e não reticulados porosos, com propriedades morfológicas e físico-químicas que podem contribuir para carrear fármacos antineoplásicos, sendo possível controlar a taxa de degradação dos mesmos e provável liberação do fármaco